In a field of general industrial equipment, a mechanical control element is driven by an electric motor. In recent years, so-called electrically mechanically integrated electric drive device, which is configured such that an electronic control unit formed from a semiconductor element etc. controlling a rotation speed and/or a rotation torque of the electric motor is integrally mounted in the electric motor, has been used.
As an example of the electrically mechanically integrated electric drive device, for instance, an electric power steering device is configured such that a turning direction and a turning torque of a steering shaft that turns by driver's operation of a steering wheel are detected, and on the basis of these detection values, the electric motor is driven so as to rotate in the same direction as the turning direction of the steering shaft, then a steering assist torque is generated. To control this electric motor, the power steering device is provided with an electronic control unit (ECU: Electronic Control Unit).
As a related art electric power steering device, for instance, an electric power steering device disclosed in Japanese Unexamined Patent Application Publication No. 2016-036246 (Patent Document 1) is known. Patent Document 1 discloses the electric power steering device configured by an electric motor unit and an electronic control unit. An electric motor of the electric motor unit is housed in a motor housing having a cylindrical portion made of aluminum alloy etc. A board of the electronic control unit on which electronic elements or components are mounted is fixed to a heat sink that is located at an opposite side to an output shaft of the electric motor in an axial direction of the motor housing and serves as a lid of an ECU housing.
The board fixed to the heat sink mounts thereon a power supply circuit unit, a power conversion circuit unit (a power module) having a power switching element such as a MOSFET and an IGBT that drive and control the electric motor, and a control circuit unit that controls the power switching element. An output terminal of the power switching element and an input terminal of the electric motor are electrically connected through bus bars.
Power is supplied to the electronic control unit fixed to the heat sink from a power supply through a connector case made of synthetic resin. Further, detection signals concerning an operating state etc. are sent to the electronic control unit from detection sensors. The connector case functions as a lid member or a cover member, and is fixed to an outer peripheral surface of the heat sink with a fixing screw so as to hermetically seal the heat sink.
As another electric drive device in which the electronic control device is integrally mounted, an electric brake and an electric hydraulic pressure controller for various kinds of hydraulic pressure control are known. In the following description, the electric power steering device from among these electric drive devices will be explained.